BARRIER PROPERTIES OF VINYLIDENE CHLORIDE COPOLYMERS

The permeability coefficients of a series of copolymers of vinylidene chloride (VDC)with methyl acrylate (MA), butyl acrylate (BA) or vinyl chloride (VC) (as comonomer)to oxygen and carbon dioxide have been measured at 1.0 MPa and 30℃, while those towater vapor have been measured at 30℃ and 100% relative humidity All the copolymersare semicrystalline. VDC/MA copolymers have lower melting temperature compared withVDC/BA copolymers, while that melting temperature of VDC/VC copolymer is higherthan that of VDC/acrylate copolymers with the same VDC content. The barrier propertyof the copolymers is predominantly controlled by crystallite, free volume fraction, andcohesive energy The permeability coefficients of VDC/MA copolymers to oxygen, carbondioxide, and water vapor were successfully correlated with the ratio of free volume tocohesive energy.     

BARRIER PROPERTY AND STRUCTURE OF ACRYLONITRILE/ACRYLIC COPOLYMERS

A series of acrylonitrile (AN) copolymers with methyl acrylate (MA) or ethyl acrylate(EA) as comonomer (5--23 wt%) was prepared by free-radical copolymerization. The per-meability coefficients of the copolymers to oxygen and carbon dioxide were measured at1.0 MPa and at 30℃, and those to water vapor also measured at 100% relative humidityand at 30℃. All the AN/acrylic copolymers are semicrystalline. As the acrylate contentincrease, the permeability coefficients of the copolymers to oxygen and carbon dioxide areincreased progressively but those to water vapor are decreased progressively The gas per-meability coefficients of the polymers were correlated with free-volume fractions or the ratioof free volume to cohesive energy.     

Simple preparation and catalytic activity of Pd particles dispersed mesoporous carbons from poly(VDC/MA) containing Pd and Y compounds

We report a simple preparation of Pd particles dispersed mesoporous carbons. The carbons were prepared by steam activation of carbonized vinylidene chloride/methyl acrylate copolymer (poly(VDC/MA)) containing yttrium acetylacetonate (Y(acac)(3)) and palladium acetylacetonate (Pd(acac)(2)). The resulting carbons consist of high contents of mesopore and uniformly dispersed fine Pd particles. We measured the catalytic activities of the carbons obtained for hydrogenation of methyl linoleate. The Pd particles dispersed in mesoporous activated carbons obtained from poly(VDC/MA) containing both Y(acac)(3) and Pd(acac)(2) showed high catalytic activities, compared with the microporous activated carbon obtained from poly(VDC/MA) containing only Pd(acac)(2). Especially Pd particles dispersed in mesoporous carbons exhibited excellent selectivity for hydrogenation of diene (methyl linoleate) to monoene (methyl oleate).     

Composition of vinylidene chloride/phenylacetylene (VDC/PA) copolymers and vinylidene chloride/methyl acrylate/phenylacetylene (VDC/MA/PA) terpolymers from analysis by 13C-NMR spectroscopy

¹³C-NMR spectroscopy has been utilized to characterize Saran polymers containing polyene segments generated by incorporating phenylacetylene (PA) units into either poly(vinylidene chloride) (PVDC) or a typical Saran copolymer of 91% vinylidene chloride (VDC) and 9% methyl acrylate (MA). The incorporation of PA could not be defined in the usual statistical way because the presence of the PA double bond in the polymer backbone appeared to cause the dehydrohalogenation of units next to it. Thus, sequences of PA next to VDC were not observed. Rather, sequences of olefinic units next to VDC units were present at a level equal to the level of PA incorporation. The level of unsaturation in the PA copolymers is approximately four times the level of PA incorporation. These observations are consistent with the random incorporation into the copolymer of PA which then initiates the dehydrohalogenation in adjacent VDC units. This dehydrohalogenation reaction appears to propagate from one unit to the next along the backbone of the polymer such that polyene segments containing the PA unit are formed.     

偏氯乙烯-氯乙烯悬浮共聚物的结晶与熔融性能

研究了聚合温度、共聚物组成、低分子助剂用量等对偏氯乙烯 (VDC) 氯乙烯 (VC)悬浮共聚树脂的结晶度、熔融峰温度的影响 ,并用Florry的聚合物熔点降低理论预测共聚树脂熔点随共聚组成、低分子助剂用量的变化规律 ,为VDC VC悬浮共聚树脂的合成工艺条件和加工性能的改善提供理论基础 .     

Ni/Al2O3催化剂上CH4三重整反应-催化剂床层温度分布

在连续流动的固定床反应装置上，考察了Ni/Al2O3催化剂上CH4三重整反应中催化剂床层的温度分布。实验在常压、750℃~950℃、2000h-1~20000h-1下进行，研究了外控炉温、空速和进料组成对催化剂床层温度分布的影响。结果表明，催化剂床层中的温度梯度较甲烷部分氧化反应平缓，在CH4/CO2/H2O/O2=50/12.5/12.5/25（摩尔比）、20000h-1下，催化剂床层中入口处温度比炉温高约80℃，出口处温度与器壁温度相当。空速越低，催化剂床层入口处温度(tmax)与炉温之差Δtmax越小(20000h-1时，Δtmax=80℃；2000h-1时，Δtmax=30℃)。当原料气中不含O2时，催化剂床层入口处没有观测到温度骤升的现象。催化剂床层温度分布出现“低谷”现象，温度最低点(tmin)比炉温低30℃~40℃。根据温度分布曲线，大体可将催化剂床层分为三个区域：富氧区、贫氧区和无氧区。富氧区内只发生燃烧反应，贫氧区内发生重整反应和部分氧化反应，无氧区内只发生重整反应。     

偏氯乙烯-丙烯腈悬浮共聚物的组成研究

研究了偏氯乙烯 丙烯腈 (VDC AN)悬浮共聚体系中AN的水溶性对单体相组成和树脂组成的影响 .结果表明 :由于AN部分地溶于水 ,使有机相AN的含量降低 ,导致共聚树脂的组成明显地不同于本体聚合模型的计算预测值 .为了准确地计算预测VDC AN共聚树脂的组成 ,本文假设溶于水的AN向有机相迁移的速度比聚合反应速度快得多 ,AN在两相的溶解分配近似为平衡态 .计算中先用描述AN在VDC/水系统中溶解分配的Marker式校正有机相AN的含量 ,然后根据校正后的AN含量用Mayo Lewis式计算预测VDC AN悬浮共聚物的组成 ,计算中有关的竞聚率值取自于文献中本体聚合的值 .计算结果与实验值一致     

Solubility of oxygen, carbon dioxide and water in semifluorinated alkanes and in perfluorooctylbromide by molecular simulation

Solubilities of oxygen, carbon dioxide and water in substituted fluorocarbons perfluoroctylethane (PFOE), perfluorohexylethane (PFHE), perfluorohexylhexane (PFHH) and perfluoroalkylbromide (PFOB) were studied by computer simulation, between 293 and 313 K at 1 bar. The solubilities do not show a marked temperature dependence, are similar in all solvents and have values of the order of 4×10⁻³ for oxygen, 2×10⁻² for carbon dioxide and 3×10⁻⁶ for water, in mole fraction. The gases are slightly less soluble in PFHE when compared with the other solvents, whereas water is slightly more soluble in this liquid. The solubilities were obtained from Henry’s law coefficients, in turn derived from residual chemical potentials of the solutes at infinite dilution obtained by molecular simulation techniques using full atomistic force fields.     

CATION/ANION MODIFIED CERIA-ZIRCONIA SOLID SOLUTIONS PROMOTED BY Pt AS CATALYSTS OF METHANE OXIDATION INTO SYNGAS BY WATER IN REVERSIBLE REDOX CYCLES

Ca and/or F-modified fluorite-like Ce-Zr-mixed oxides have been prepared by Pechinis method. The bulk structure of samples was characterized by XRD, EXAFS and FTIRS of the lattice modes. The surface properties were studied by SIMS and FTIRS of adsorbed CO and surface hydroxyls. The specific reactivity of the surface oxygen, its amount, coefficients of bulk and near-surface diffusion, as dependent upon the sample composition and temperature, were estimated using sample reduction by CO in the pulse/flow mode. Insertion of fluorine into the lattice results in decreasing the degree of oxygen polyhedra distortion, thus decreasing the amount of reactive oxygen and diffusion coefficients. Calcium and Pt addition counteracts this effect. At 500^oC for Pt-supported Ce-Zr-O samples including those modified by Ca and F, the lattice oxygen is easily removed by methane generating CO and hydrogen with high selectivity. Reoxidation of reduced samples by water or carbon dioxide at the same temperature restores the oxygen capacity producing more hydrogen or carbon monoxide.     

Hydrophobic Properties of Thin Films of Comb-Shaped Perfluorohexylethyl Methacrylate-Polydimethylsiloxane Copolymers Deposited from Supercritical Carbon Dioxide Solutions

Comb-shaped copolymers of perfluorohexylethyl methacrylate and methacryloxypropyl-terminated polydimethylsiloxane are synthesized by radical polymerization in supercritical carbon dioxide, solubility of the copolymers in supercritical carbon dioxide is studied, and hydrophobic properties of thin films obtained via precipitation of the copolymers from trifluorotrichloroethane and supercritical carbon dioxide solutions on substrates are examined. On the basis of water and dimethyl sulfoxide contact angle measurements, the specific free surface energy of the formed films is calculated. It is shown that the thin films of the copolymers have a lower surface energy and are characterized by a smaller water contact angle hysteresis than the films based on homopolymer poly(perfluorohexylethyl methacrylate). A comparative testing of coatings based on the homopolymer and copolymer deposited from solutions in supercritical carbon dioxide on the surface of nylon fabrics is performed. It is found that copolymer-coated fabrics have on average higher water contact angles.     

二氧化碳/1,2-环氧丁烷/ε-己内酯的三元共聚合和表征

以高聚物负载型双金属负离子配位化合物PBM为催化剂,通过二氧化碳(CO2),1,2-环氧丁烷(BO)与ε-己内酯(CL)的三元开环共聚合反应,得到三元共聚物,脂肪族聚碳酸酯(PBCL).对PBCL进行了FTIR1、H-NMR1、3C-NMR、DSC和WAXD等表征,并考察了反应单体比例及反应时间对共聚物性能的影响.结果表明,由于ε-己内酯开环共聚,引入了易水解的羧酸酯单元,PBCL的降解速度和玻璃化转变温度较二氧化碳-环氧丁烷的二元共聚物(PBC)得到了有效地提高.同时,PBCL相对于聚己内酯(PCL)玻璃化转变温度和降解速度明显改善,且PBCL为非晶结构.     

Degradation of vinylidene chloride/methyl acrylate/phenylacetylene (VDC/MA/PA) terpolymers. Effect of internal unsaturation on the stability of Saran copolymers

The thermal degradation of vinylidene chloride/methyl acrylate/phenylacetylene (VDC/MA/PA) terpolymers containing a constant 9 wt % methyl acrylate and small but varying amounts of phenylacetylene has been examined in the solid phase and in bibenzyl solution. Thermally promoted degradative dehydrochlorination, largely uncomplicated by methyl chloride formation, readily occurs at temperatures approaching 200°C. Incorporation of phenylacetylene into the polymer structure greatly facilitates degradative dehydrochlorination. Indeed, the presence of phenylacetylene induces the formation of polyene segments during the polymerization so that all the terpolymers, even at very low phenylacetylene loading, are tan in color. The decreased stability of polymers containing internal unsaturation arises from an increased rate of initiation for the degradation reaction. The propagation rate is largely unaffected by the level of unsaturation initially present in the polymer. Thus random double bonds have been identified as the principal defect sites responsible for the facile degradation of Saran copolymers. Species which promote the degradation of Saran polymers probably do so by facilitating the introduction of double bonds into the structure. The ratio of hydrogen chloride to stilbene formed for degradation of the terpolymers in bibenzyl solution is ca. 35:1. This is strongly reminiscent of PVDC degradation and suggests that for degradation of either the homopolymer or Saran copolymers the chain-carrying allylic radical pair does not dissociate to any appreciable extent as dehydrochlorination occurs.     

在位红外光谱法研究丙烯腈、二丙酮丙烯酰胺和丙烯酸甲酯三元共聚物的低温热解

本文用傅里叶变换红外光谱法在位连续测定了丙烯腈(AN)、二丙酮丙烯酰胺(DAA)和丙烯酸甲酯(MA)三元共聚物在不同气氛中低温热解时化学结构的变化。据光谱峰的变化规律,发现共聚物在空气中热解时脱氢和氧化主要在环化反应发生之后;在氧气中热解时脱氢和氧化主要发生在环化反应之前;在氮气中热解时仅有环化和脱氢反应。在比较各气氛中的成环序列长度时,在氮气中热解环序列在275℃以下稍短;275℃以上稍长。共聚物羰基增加的相对含量与热解时间的平方根成正比。     

Enthalpies of absorption and solubility of CO2 in aqueous solutions of methyldiethanolamine

A flow mixing unit using a SETARAM C-80 calorimeter, developed for measuring the enthalpy of solution of two fluids, has been used to measure enthalpies of absorption of carbon dioxide in a 30 wt.% aqueous solution of methyldiethanolamine (MDEA) at three temperatures 313.15, 353.15, 393.15 K and three pressures 2.0, 5.0, 10.0 MPa. We have established that the effect measured by calorimetry corresponds not only to the absorption of CO₂ in the aqueous solution but also to the vaporisation of water into the carbon dioxide depending on the temperature and the pressure of the experiment. The enthalpies measured by calorimetry were compared with those calculated from solubility measurements and a reasonable agreement within the accuracy of measurement and calculation was found.     

The gas permeability and packing density of copolymers of methacryloxypropyltris (trimethylsiloxy) silane and methylmethacrylate

A series of random copolymers of methylmethacrylate and methacryloxypropyltris (trimethylsiloxy) silane were synthesized by free radical polymerization under ultraviolet light. The permeabilities of these copolymers to carbon dioxide, oxygen, and nitrogen were determined and correlated with the packing densities of the polymers. Correlation between the permeability and permselectivity of these copolymers is also addressed.     

先锋褐煤在水热处理过程中的结构演绎

以先锋褐煤(XF)为原料,在高压反应釜中考察了水热处理过程中褐煤的结构变化,通过13C固体核磁共振(NM R)和傅里叶变换红外光谱进行了分析表征。结果表明,在低于240℃的水热处理条件下,煤有机分子结构中的弱化学键有一定断裂,含氧官能团逐步减少;水中氢以离子形态迁移至褐煤中,处理后褐煤结构中甲基比例先增加后减少,次甲基比例由原煤的4.80%增加至XF-240的13.16%;释放的气体中主要是CO_2,烃类气体组分随处理温度的升高略有增加。当水热处理温度高于240℃时,褐煤中部分共价键开始断裂,释放的烃类气体(C1-4)由240℃时的2.13%增加至300℃时的8.59%,脂肪碳比例由XF-240的44.83%降低至XF-300的39.49%,与氧连接的碳比例由XF-240的12.57%降低至XF-300的1.49%。水热处理对褐煤的脱氧提质效果显著,300℃时氧含量降低约30%,芳香碳比例增加至60.50%,比原煤提高19%。     

聚乙烯-g-聚苯乙烯对线性低密度聚乙烯/聚苯乙烯共混物机械性能和发泡行为的影响

以通过开环易位聚合、加氢反应和原子转移自由基聚合技术结合制备的聚乙烯-g-聚苯乙烯(PE-g-PS)作为增容剂,研究了加入不同PS支链长度的PE-g-PS对于线性低密度聚乙烯/聚苯乙烯(LLDPE/PS)共混物的机械性能和发泡行为的影响。 以典型组成m(LLDPE):m(PS)=70:30共混物为例,考察了PE-g-PS对共混物拉伸性能的影响。 相对于二元共混物,增容剂的加入使得断裂伸长率、拉伸强度和屈服强度皆提高,且含长PS支链的增容体系提高更明显。 采用超临界CO₂釜式发泡工艺,考察了PE-g-PS中PS支链长度对共混物发泡行为的影响。 结果表明,相对于短PS支链体系,加入PE-g-PS_1.59k(PS相对分子质量为1590)后的泡孔结构更加均一,完全没有“缝隙”形貌的出现。 当发泡温度降至80 ℃时,即使存在LLDPE发泡空间限制作用(LLDPE无法发泡),加入支链长度更长的PE-g-PS_1.59k后泡孔分布也更加均一。     

锆茂均相催化体系催化乙烯与降冰片烯共聚合的研究

锆茂均相催化体系催化乙烯与降冰片烯共聚合的研究谢光华，王金梅，张盛庆（中国科学院化学研究所，北京，１０００８０）关键词锆茂均相催化体系，乙烯，降冰片烯，共聚合金属二茂基化合物与甲基铝氧烷（ＭｅｔｈｙｌａｌｕｎｕｎｏｘａｎｅＭＡＯ）组成以甲苯为溶剂的均...     

Transport of water and gases through EVA copolymer films,EVA70/PVC,and EVA70/PVC/gluten blends

The transport of water vapor and gases (oxygen or carbon dioxide) through poly(ethylene‐co‐vinyl acetate) (EVA) films of different VA contents and through EVA₇₀/PVC and EVA₇₀/PVC/gluten blend films, was analysed by permeation measurements. In the case of water, a plasticization effect on the material is observed for EVA films with more than 33percnt; wt. of VA content and also for the EVA₇₀/PVC blend. For EVA of 19 wt.percnt; VA, there is no plasticization, while for LDPE (low density polyethylene) and EVA of 4.5 wt.percnt; VA, the water diffusion coefficient decreases with increasing the water content. A negative plasticization effect was accounted for by an empirical model and attributed to the formation of water clusters in the non polar polymers. The increase in water sorption extent with the VA content leads to a steady increase in the water permeability in the EVA copolymers while for the EVA₇₀/PVC blend, the reduced water permeability is explained by the interaction between chlorinated units and polar groups. In the case of gas permeation, both for O₂ and CO₂ and whatever the VA content of the copolymer used, the experimental curves are characterized by a constant diffusion coefficient. This result is not surprising as it is generally admitted that, gases sorb into rubbery polymers according to Henry's law. By mixing PVC with the EVA of 70percnt; wt. VA, the diffusion coefficients of CO₂ and O₂ are greatly reduced (6 times).     

Effect of UV Irradiation on Gas Permeability in Heterophasic Ethylene-Propylene Copolymer Films

Abstract

The permeability variations of carbon dioxide, oxygen, and nitrogen through isotactic polypropylene, heterophasic ethylene-propylene (E-P) copolymers, and polyethylene films were measured during photo-oxidation using polychromatic light at 60°C in air. For polypropylenebased samples the permeability decreases with increasing photooxidation, whereas for polyethylene and an elastomeric fraction from a heterophasic E-P copolymer an increase in permeability with photooxidation is observed.